The 61-kilometre line section between Innertkirchen and Mettlen is to be replaced and upgraded from 220 to 380 kilovolts. The Swiss Federal Office of Energy decided on the Glaubenberg planning territory at the end of 2022. Swissgrid will now devise suggestions for corridors within the planning territory.
Most of the 61-kilometre extra-high-voltage line between Innertkirchen and Mettlen is over 70 years old and needs to be replaced. At the same time, the line voltage will be upgraded from the existing 220 kV to 380 kV along its entire length. This upgrade is an important project within Swissgrid’s implementation of «Strategic Grid 2025».
Expanding the amount of electricity produced from hydropower is a central pillar of the Energy Strategy 2050. The increase in capacity between Innertkirchen and Mettlen is necessary to be able to transport the growing volume of electricity generated by the Oberhasli power plants and the Valais and Ticino hydroelectric power plants to the Swiss Central Plateau. Distributing energy flows along several north-south axes also increases grid stability. The Innertkirchen – Mettlen grid project therefore not only supports the expansion of renewable hydropower, it also ensures Switzerland’s security of supply.
In mid-2021, Swissgrid applied to the Swiss Federal Office of Energy to establish a planning territory between Innertkirchen and Mettlen in the federal government’s sectoral plan for transmission lines. Planning territories are geographic areas within which a planning corridor, including transmission technology (underground cable, overhead line or combined options), can then be chosen at a subsequent stage of the project. To this end, Swissgrid examined three partly overlapping planning territories.
Both of the submitted variants have specific advantages and disadvantages with respect to regional planning, the environment, technology and economic viability. The monitoring group of the Swiss Federal Office of Energy (SFOE) believes that the Glaubenberg planning territory is the best option. Firstly, it touches fewer settlement areas and involves fewer obstacles than the other options. Secondly, it is much shorter than the planning territory via Entlebuch and so has less of an impact on the ground, the natural environment and the landscape, requires less construction material and has lower energy losses and costs. At the end of 2022, the SFOE therefore decided on the Glaubenberg planning territory, with minor adjustments in relation to the variant submitted by Swissgrid.
The section between Mettlen and Hellbühl (Littau) is considered separately. It was upgraded to 380 kV in 1990, but is currently operating at just 220 kV. The Innertkirchen – Mettlen and Bickigen – Mettlen lines approach one another to the west of Rothenburg, from where they are bundled in the section to Mettlen. With this in mind, it makes sense to consider both lines together in this section in order to provide permanent relief for the settlement area. Swissgrid will therefore review the line routing in this area as part of the planned Bickigen – Mettlen line renovation. The line lead-in for the Innertkirchen substation will be considered separately within the Innertkirchen – Mettlen sectoral plan process: two additional transmission lines run parallel to the Innertkirchen – Mettlen line along a roughly two-kilometre section. As all three lines pass through the settlement area, the only option in this section is to install an underground cable in a tunnel. As all three lines pass through the settlement area, the only option in this section is to install an underground cable.
The next stage of the sectoral plan process is for Swissgrid to devise suggestions for corridors within the specified planning territory. After that, a monitoring group appointed by the SFOE will come together with the federal authorities, the affected cantons and environmental associations to discuss and assess the planning corridor variants developed by Swissgrid. The monitoring group’s recommendation then continues on to the public collaboration stage. The Federal Council is expected to define the planning corridor with a specific transmission technology (overhead line, underground cable or a combined solution) between Innertkirchen and Mettlen in autumn 2025. Ideally, the renewal of the Innertkirchen – Mettlen extra-high-voltage grid will be completed by 2035. After that, the existing line, parts of which run through the settlement area, will be removed.
